PROJECT SUMMARY/ABSTRACT The goal of this project is to write a book that addresses the responsibilities and obligations between siblings in health care. The reason to care about siblings is that they may be the longest relationship of our lives. It is a relationship that (usually but not always) involves a shared upbringing, shared genes and shared secrets, and they are often the most significant relationships with respect to our psychological and emotional development. The reason to care about sibling responsibilities and obligations in health care is that a diagnosis of a health problem in one sibling has health implications for the others. Sometimes it may mean that the other siblings are at increased risk for the same disorder or condition (due to genetics or environment). Other times it may mean that family resources and energy are disproportionately focused on the family member with the disorder or condition to the disappointment of the other siblings. It may also lead to a request or demand for sibling help?from information sharing to tissue or organ donation to physical care giving or proxy decision- making. The question, ?What are our obligations to our siblings??, remains largely unanswered in the philosophical literature and in the bioethics literature generally, and not just specifically in health care, despite the fact that most of us are born and raised in families with more than one child (at least in the United States (US) and the fact that these relationships persist, albeit with changing degrees of intensity, proximity, and mutuality across the lifespan. To write this book, I need to develop a normative framework with which to think about sibling relationships, obligations and responsibilities that can accommodate great variability and diversity in families and family structures. Then, the utility of this framework needs to be evaluated in various clinical settings with siblings of different degrees of intimacy, biological relatedness and proximity of age. I will use cases in five areas of health care: 1) solid organ and tissue transplantation; 2) assisted reproduction; 3) genetics; 4) human experimentation; and 5) decision making for and with siblings with disabilities. The methodology will involve an ethical analysis of case studies and classic problems that will be analyzed to achieve reflective equilibrium between the normative theory and judgments about the cases. Cases and classic problems are an important component of the book because they facilitate 1) comprehension of the complex issues and highlight the social context of intrafamilial health care responsibilities and obligations; and 2) appeal to a broad audience of health care professionals, bioethicists and other social scientists interested in sibling relationships.